I. Field of the Invention
This invention relates generally to fluid handling apparatus and more specifically to the improved design of a multi-piston/cylinder pump for delivering fluids at relatively high pressure, the pump being designed for ease of assembly and subsequent repair, all as will be set forth in greater particularity hereinbelow.
II. Description of the Prior Art
Multi-piston pumps, as such, are known in the art. Typical are the structures set forth in the Dunn et al U.S. Pat. No. 3,747,478 and the Pareja U.S. Pat. No. 4,032,263 which are each assigned to the same assignee as the instant invention. Each of these patents describes a high pressure, three-cylinder pump in which a three-lobed cam shaft is disposed in an oilfilled crankcase in cooperative driving relationship with the pistons to provide pressure strokes thereto in a desired phase relationship, the suction stroke of the piston being provided by return springs disposed between a member secured to the cylinder housing and the pistons, which maintain the ends of the pistons in contact with the lobes on the camshaft. Since these springs are repetitively compressed and allowed to expand at a frequency determined by the angular velocity of the camshaft, they are subject to fatigue failure after prolonged use.
These prior art structures further include sealing means disposed between the cylinder walls and the pistons to prevent leakage of the fluid being pumped between the cylinder walls and the pistons during the pressure strokes. Since there must necessarily be relative motion between the pistons and the seals, the seals are the most vulnerable part of the pump as far as wear and attendant repair is concerned.